Amino-ether gas treating process



ANJtYG-ETHER GAS TREATING PROCESS Clyde L. Biohm, Los Angeles, and Fred C. Riesenfeld, Hollywood, Caliii, assignors to The Floor Corporation, Los Angeles, Calif., a corporation of California No Drawing, Application November 10, 1950, Serial No. 195,126

Claims. (Cl. 232) This invention has to do with the treatment of gaseous mixtures for the removal of acidic constituents, and sometimes also moisture, and is directed particularly to the extraction of such acid gases as hydrogen sulfide and carbon dioxide from wet or dry hydrocarbon gases of which natural gas and refinery gases are typical.

A general practice has been to treat such gases with solutions of organic amines which are reactive with the acid gases and can be regenerated for reuse by heating to temperatures suificient to drive oil? the absorbed acidic constituents. When it has been desired to dehydrate the gaseous mixture simultaneously with the acid gas removal, the prevalent practice has been to treat the gas with an amine solution containing also a polyhydric alcohol such as diethylene glycol. In the conventional plant cycle, the lean absorbent solution is passed downwardly through a contactor column in intimate mixture with the gas stream flowing upwardly therethrough, the rich absorbent is passed to a still wherein the solution is heated, frequently in the presence of stripping steam, to release the absorbed acidic gases and any moisture absorbed in the contactor, following which the resulting lean solution is cooled and returned to the contactor.

Various factors enter into the practical economics of the operation of this type of plant, among which are the required amino-to-gas ratio, or amine circulation rate, required for purification of the gas, amine losses from the contactor, the costs of stripping in the still, and corresponding factors applying to moisture absorptive absorbents where both moisture and acid gases are to be removed. The present invention has for its general object to improve the economic and efiiciency aspects of the treating system with respect to those conditions mentioned, and specifically by providing for an important reduction of the required amine-to-gas ratio and amine circulation rate, reduction of costly amine losses from the contactor, reduced steam requirements in the still, and by ice as such non-acid gas absorbent dehydrating liquids as diethylene glycol.

The invention is predicated upon the use as an acid gas absorbent, and also as a moisture absorbent where the gas under treatment requires dehydration, of a suitable compound in the class of the hydroxy amino alkyl ethers having the general formula:

x=2 to 3 3 :1 to 4 z=2 to 3 As illustrative of particular hydroxy amino ethers suitable for acid gas absorption, with or without dehydration, and having those advantages mentioned above, are 5,18- hydroxy amino ethyl ether For purposes of description, we refer hereinafter to the use of 5,5 hydroxy amino ethyl ether as a typical and specific example of the hydroxy amino ethers contemplated.

As an illustration, treatment of a typical natural gas containing carbon dioxide and hydrogen sulfide with a 95% solution in water of tiff-hydroxy amino ethyl ether (at 550 p. s. i. g. pressure in the contactor) will produce a treated gas containing less than 0.25 grain of hydrogen sulfide per 100 SCF and less than 0.1% carbon dioxide while absorbing volumes of acid gas (H28 and CO2) per volume of solution circulated; whereas a typical commercially used mixture of monoethanolamine, diethylene glycol, and Water will produce a treated gas of comparable purity and degree of dehydration while absorbing up to only 32 volumes of acid gas per volume of solutioncirculated. Thus a treating plant using the hydroxy amino ether solution would require only about of the liquid circulation of a comparable plant employing monoethanolamine as the acid gas absorbent and diethylene glycol as the moisture absorbent.

The following table shows comparative results in treating gaseous mixtures containing carbon dioxide and hydrogen sulfide, with fi,fi-amino hydroxy ethyl ether and ordinary monothanolamine absorbents. Primarily the comparison is made to show the advantages with respect to the absorbent and absorbent acid gas volume ratio, and amine losses, resulting from the use of the amino ether:

Operating Conditions Results Inlet Gas Nominal Solution Concentration Outlet Gas Absorbent W Run Absorb- Acid Gas Lost as O e11: Absorbed Vapor in on en t Ab b Diethyl- Amine H s by S0111. Gas F 001, His, ene Water, Normb G02, Grgm/ (Net), a), $9 Percent Percent Percent ggg g Percen? ity Percent 100 s. c.f. VOL/Vol g g s. c. f.

550 5. 2 0. 44 0 5. 9. 5 0. 0 0.19 55 0.06 550 3. 9 0.68 25 70 5 4. 4 0. 0 0.17 32 0. 50 550 5. 4 0. 91 45 0 55 4. 4 0. 0 0.11 43 0. 01 40 5.6 7.0 52 0 4s 5. 2 0.0 1.1 as 0.08 to 3.6 6.9 as 0 e7 5. s 0. 0 1. 0 as 3. 2

EIQEE=B,5-Hydroxy amino ethyl ether.

MEA=Monoethanolamine the employment of a single compound or aqueous solution thereof, having the capacity for both acid gas absorption (with the attendant advantages mentioned) and moisture absorption with at least the same efiectiveness In run No. l, the amino ether is compared with the use in run No. 2 of a typical monoethanolamine solution, in that both are dehydrating systems containing 5% water. It is noted that the amino ether solution absorbs 72% ot the amino ether and monoethanolamine, in treating gas i containing more hydrogen sulfide than carbon dioxide. Comparable treating efficiencies were obtained, while absorbent losses from the amino ether solution were only about one-fortieth of the monoethanolamine loss.

Speaking generally of the contemplated amino ethers in the general class hereinbefore defined, it is preferred to use those amino ethers having a viscosity of less than 100 centipoises. at 25 C., a vapor pressure not exceeding 0.1

im} fm t r a .5 a a o n Poin n he an f. 7 to 3 0 at o m r P s re As previously indicated, substantial operating expense may be occasioned by the losses of amine from the contactor in the treated gas stream. By reason of its low vapor pressure as compared with the vapor pressure of the more volatile amines customarily employed and having comparable absorption efliciencies, the amino ether remains in the system with comparatively low losses from the contactor.

Qbviously the possibility of using a single compound for both acid gas and moisture absorption in a single treating step or stage, presents important advantages in that no requirements for maintaining proper proportions of separate acid gas and moisture absorbents are involved, and as previously explained, a lesser quantity or circulation rate poses of a combination absorbent such as monoethanol:

and glycol circulated at a higher rate.

1 Greater: economies in the still operation are possible by r ason oi h hi her a d a an moisture concentration in rich solution, all of which tend to decrease the heat requirements, or the amounts of steam customarilyemployed, to aid stripping in the still,

As to 7 operating. conditions, the concentration of the amino ether, in the absorbent solution may vary dependent upon such considerations as whether the gas being treated re uir s. eh d at on F r pu o f c gas removal, the amino ether (and again typically ,B,;3-hydroxy amino ethyl ether) maybe used in aqueous, solutions in concentrations ranging between about 20% to 95 %s by volume of the. solution. For purposes of dehydration the amino et e sw a n ma be t n x s of nd 'r sa n e e s r o 9,5%- The containe temperatures and pressures may be of the order customarily employed in amine treating plants, typically solution inlet temperatures between F. to 130 F. with pressures ranging from slightly above atmospheric pressure to within the 600 to 800 pound range. The still temperature may be, governed simply bythc heating of the rich solutionrequired to drive off the absorbed acid gases, leaving.

in the stripped solution the. water content desired for its 7 use as alean absorbent.

We claim: 1 1. The process of treating a gaseous mixture stream for the removal-therefrom of an acidic gas of the group consisting of hydrogen sulfide and; carbon dioxide, that ineludes contacting said mixture with an absorbent. containing an amino ether having the general formula absorbed acid gas, and again contacting said gaseous stream with the regenerated amino ether. 7

2. The process as defined by claim 1, in which said absorbent consists of an aqueous solution of the hydroxy amino ether.

3. The process as defined by claim 1, in which said gaseous mixture contains moisture, said moisture is absorbed by the amino ether, and the absorbed moisture is liberated 'by said heating of the hydroxy amino ether.

4. The process so defined by claim 3, in which said absorbent consists of a solution containing water and in excess of of the hydroxy amino ether.

5. The process as defined by claim 1, in which said gaseous mixture contains moisture, and said absorbent contains water and a polyhydric alcohol in addition to the hydroxy amino ether.

6. The process of treating a gaseous mixture stream for the removal therefrom of an acidic gas of the group consisting of hydrogen sulfide and carbon dioxide, that includes contacting said mixture with an absorbent containing p -hydroxy amino ethyl ether and absorbing the acid gas in the amino ether, separately heating and regenerating the absorbent, and again contacting said gaseous stream with the regenerated absorbent.

7. The process of treating a gaseous mixture stream for the removal therefrom of an acidic gas of the group consisting of hydrogen sulfide and carbon dioxide, that includes contacting said mixture with an absorbent containing water and between about 20 to of 6,6 hydroxy amino ethyl ether and absorbing the acid gas in the amino ether, separately heating and regenerating the absorbent, and again contacting said gaseous stream with the regenerated absorbent.

8. The process of treating a gaseous mixture stream fth Single amino ether absorbent, will Serve n h 2 3 for the removal therefrom of moisture and an acid gas of the group consisting of hydrogen sulfide and carbon dioxide, that includescon'tacting said mixture with an absorbent containing water and" in excess of 90% 13,5 hydroxy amino alkyl ether and absorbing moisture and '3' the acid gas in the absorbent, separately heating and regenerating the absorbent, and again contacting said gaseous stream with the regenerated absorbent.

9. The process of treating a gaseous mixture stream for the removal therefrom of an acidic gas of the group consisting of hydrogen sulfide and carbon dioxide, that 7 includes contacting said mixture with an absorbent containing ,8'-hydroxy (B-amino ethoxy) ethyl ether and absorbing the acid gas in the amino ether, separately heating and regenerating the absorbent, and again con- 1 tacting said gaseous stream with the regenerated absorbent.

' 10. The process of treating a gaseous mixture stream for the removal therefrom of an acidic gas of the group consisting of hydrogen sulfide and carbon dioxide, that includes contactingsaid mixture with an absorbent containing water and between about 20 to 95% of fi-hydroxy (ft-amino ethoxy), ethyl ether and absorbing the 'acid gasin the hydroxy-amino ether, separately heating and regenerating the absorbent, and again contacting said gaseous, stream with the regenerated absorbent.

References ("Zited in the file of this patent U Nl-TED STATES PATENTS 2,065,112 Bottoms Dec. 22, 1936 2,139,122 Hass Dec. 6, 1938 2,139,375 Millar- Dec. 6, 1938 2,177,068 Hutchinson Oct. 24, 'l 939 FOREIGN PATENTS 7 344,786 Great Britain Mar. 4, 1931 410,848 Great Britain May 23, 193 

1. THE PROCESS OF TREATING A GASEOUS MIXTURE STREAM FOR THE REMOVAL THEREFROM OF AN ACIDIC GAS OF THE GROUP CONSISTING OF HYDROGEN SULFIDE AND CARBON DIOXIDE, THAT ININCLUDES CONTACTING SAID MIXTURE WITH AN ABSORBENT CONTAINING AN AMINO ETHER HAVING THE GENERAL FORMULA 